Production of nickel powder



Patented Feb. 25, 1941 I PATENT OFFICE PRODUCTION or NICKEL rownnn Charles Leigh Mantell, Manhasset, N. Y., assignor to Hardy Metallurgical Company, New York, N. Y., a corporation of Delaware N0 Drawing. Application April 6, 1938,

Serial No. 200,418

11 Claims.

This invention relates to the production of nickel in finely divided form, andparticularly to the production of nickel powder by electrolytic deposition fro-m a solution. 5 It. has been customary heretofore to plate nickel out of solution in massive form, employing acidified aqueous baths of nickel salt. Efforts to produce a finely divided deposit of nickel by electrolysis of such baths have not been successful, the nickel tending to deposit in massive form even at relatively high current density, so that heretofore nickel powders have been produced by pyrometallurgical J processes, usually from nickel carbonyl.

However, as a result of my investigations, 1 have discovered a method of depositing nickel in, finely divided form, which method is simple and reliable, 1

does not require excessive current densities or excessivepower consumption and employs an inexpensive electrolyte. In the practice of my invention, I employ an alkalinev aqueous solution containing nickel in the form of nickelammonium ions, and endeavor to maintain the at a minimum.

In brief, the method of my invention for producing nickel in finely divided form comprises subjecting to electrolysis in anelectrolytic cell containing an anode and a cathode,-an alkaline aqueous solution consisting essentially of alkali ions, nickel-ammonium ions, hydroxyl ions and chloride ions, whereby the nickel tends to deposit at the cathode in powder form or in a condition in which it is easily reduced to powder.

form. As indicated hereinbefore, it is desirable to maintain the proportion of nickel-ammonium ions to nickel ions in the solution relatively high during electrolysis.

In the presently preferred practice of my invention, the operation is begun with an electrolyte in the form of an alkaline aqueous solution of ammonium chloride. A soluble nickel bearing anode is employed so that the nickel tends to dissolve therefrom and enter the solution in the form of the nickel-ammonium complex. The nickel deposits from the solution in finely-divided form at a cathode, which preferably is made of sheet nickel.

I prefer to employ an ammonium chloride solution containing at least 200 grams perliter of ammonium chloride. However, saturated solutions of ammonium chloride may be employed, the saturation point for ammonium chloride at 0 C.

being 297 grams per liter. At a temperature of concentration of true nickelions in the solution 20 C the bath may contain as much as 300 grams perliter of ammonium chloride.

The bath must be alkaline and the alkalinity preferably is obtained by adding from 1 to 3 grams per liter of sodium hydroxide or its equivalent. 5

The temperature of the bath should range from 20 to 30 C. for'best results. The nickel anode may be cast or electrolytically deposited metal. Anode current densities may vary from as low as 10 amperes per square foot-to as high as amperes per. square foot. For the sake of electrical economy, anode current densities of from '10 to 20 amperes per square foot are preferred.

The cathodepreferably should be of-smooth sheet nickel and cathode current densities may vary from 20 to 120 amperes per square foot. However, cathode current densities of the order of 20 to 30 amperes per square foot are preferred.

In operation, the bath preferably should contain substantially no nickel ions and at all times the nickel ion concentration should be kept low. A low; concentration of nickel ions in the solution may be obtained by adjusting the relationship between the current density at the anode and the current density'of the cathode so that the nickel deposits at the cathode at substantially the same rate and at worst, at only a slightly lower rate than it goes into the solution at the anode.

Due to the presence of the nickel-ammonium complex in the electrolyte, it attains a blue color. In practice proper concentration of nickelammonium ions-in. the solution can be judged by the color thereof. In the event that a substantial concentration of nickel ions tends to develop in the electrolyte (and this may be determined either through a change in the color of the electrolyte orby chemical analysis) it is desirable to decrease the rate of anode corrosion. This is done conveniently by introducing insoluble anodes into 0 the bath along with the nickel bearing anodes. Thus, carbon or graphite electrodes may be used for insoluble anodes. By increasing the ratio of exposed surface of insoluble anodes to the exposed surface of soluble nickel anodes in the bath, it is possible to decrease the rate of solution of nickel at the anode to a point where the deposition rate at the cathode exceeds it. In this way, the tendency of the nickel to build up in solution and ionize as' nickel ions instead of 50 nickel-ammonium ions, is overcome. a

At the preferred anode and cathode current densities, i. e., an anode current density of 10 to 20 amperes per square foot and a cathode current-density in excess of 20 amperes per square foot, the electrolyte (which originally is colorless and contains no nickel) assumes a light blue shade due to the iormation or the nickelammonium complex. The nickel ammonium complex salt in the solution has very little tendency to form nickel ions because the primary ionization of the salt produces ammonium ions, and only a secondary ionization (taking place to a much smaller extent than the first) produces nickel ions.

In operation, under the conditions hereinbefore prescribed, the powdery deposit of nickel'iormed at the cathode is relatively adherent so that the cathode may be lifted out oi the solution without disturbing the deposit. The deposit may be then removed from the cathode by flushing, washing or scraping after which the cathode may be returned to the cell. The powdery deposit is freed irom all lectrolyte by water washing, then physically separated from the water by any of the conventional methods such as filtration, centrifuging, decanting and the like, and thereafter dried and subjected to slight crushing to hydraulic classification.

The practice of my invention will be more thoroughly understood in the light of the following detailed description of a presently preferred practice, taken in conJunction with the accompanying table which shows the conditions pertaining to the operation and the results obtained.

cell an aqueous solution containing 300 grams per liter of ammonium chloride and 2' grams per liter of sodium hydroxid. An anode of electrolytically deposited nickel was placed in the cell in contact with the electrolyte, the cathode being a piece .of pure 'sheet nickel. Direct current was passed through the cell under the conditions indicated in the table and in all instances nickel deposited at the cathode in the form of a very fine powder. A small amount of the nickel powder tended to slough oil the cathode and deposit in the bottom of the tank. In Test I, the deposit at the cathode was very easy to remove, the cathode current density in this instance being 20 amperes per square foot. At higher current densities, i. e., in Tests II, III, IV, V and VI, the powder deposit tended to adhere more firmly to the cathode and it was noted that as the current density was increased, it was correspondingly harder to remove the powder deposit from the cathode. It will be' noted that in Test I, operating at a current density of 20 amperes per square foot, the lowest voltage was obtained together with the maximum deposit. Moreover, thedeposit obtained in Test No. I was more easily ground than the deposit obtained in other instances.

It is not essential that the nickel ammonium complex ions be obtained through solution of a soluble nickel anode. Thus, for example, it is possible to obtain a satisfactory deposit of nickel powder by carrying on the electrolysis of the solution of the complex nickel ammonium salt however this salt be derived.

I claim:

l. A method of producing nickel in finely divided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solutionconsisting essentially oi alkali ions, nickel-ammonium ions, hydroxyl ions, and chloride ions whereby the nickel tends to be dis- Test No.

I II III IV V VI 1 12 38 l/12/38 l/l2/38 l/l2/38 1/12/38 300 300 300 300 300 2 2 2 2 2 2000 2000 2000 2000 2000 3. 12 3. 12 3. l2 3. 12 3. 12 1. 1. 51 l. 49 1. 62 1. 72 Elec. nicks; Elec. nicke Elec. nicke; Elec. nicke; Elcc. nickel v 2 square inches" 43. 2 2i. 6 14. 4 10. 8 8. 6 7, 2 Anode mrrent densityfluam res per square foot" 10 20 30 40 0 1664. 5 778. 0 407. 5 429. 5 445. 0 c 338. 0 1035.5 758. 5 can. 0 410. 0 42s. 0 319. o 19. 0 19. 5 18. 6 19. 5 19. 0 19. 0 0 Sheet nickel Bhcet nickel Sheet nickel Sheet nickel Sheet nickel Sheet nickel N0 oi ti 1 V 1 1 1 l l P arm 7 v nare 21.6 10.8 7.2 5.4 4.3 3.6 Cathode current density amperes per square loot. 20 .40 0 weight ofcathodes .grams l6. 8 11. 4 8. l 9. 5 11. 3 ll. 3 Final weight of cathodes.-. do 29. 2 23. 3 12.9 18.0 20. 7 20.6 Cathode wel t gain 12. 4 11. 9 4. 8 8. 5 0. 4 9. 3 v1.0 .6 5.1 1.8 1.0 1.3 13. 4 l2. 5 9. 9 10. 3 10. 4 10. 6 1.5 1.5 1.6 1.5 1.5 1.5 23. 5 2A 24 23 24 24 7 7 7 7 7 7 56. 0 52. 3 41. 4 43. l 43. 5 43. 9 1. 05 l. 13 l. 57 1. 41 1.61- 1. 56 ,.95 -.88 .64 .71 .62 .64 Pe -cant NI 97. 47

T deposit: The deposit in all cases was in the fornioi a very fine powder on the cathode with very little deposit in the bottom of the he deposit in Test No. Ivory easy to remove. It was noted that as the C. D. was increased (Tests 11 to V1) it was correspondemarks: It is to be noted that Test I, running at the lowest 0. D., used the least voltage and gave the maximum deposit. Furthermore,

R this deposit was the easiest to grind.

In the examples reported in the table, the operation was started by placing in an electrolytic solved from the anode and deposited at the cathode in finely divided form.

2. A method of producing nickel in finely di vided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solution containing originally at least 200 grams of ammonium chloride per liter and consisting essentially of alkali ions, nickelarnmonium ions, hydroxyl ions, and chloride ions.

3. A method of producing nickel in finely divided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solution containing originally at least 200 grams of ammonium chloride per liter l5 and consisting essentially of alkali ions, nickelammonium ions, hydroxyl ions, and chlorideions,

and maintaining a cathode current density of at least amperes per square foot. A 1

4. A method of producing nickel-in finely di- 20 vided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solution containing at least originally from 200 to 300 grams per liter of ammonium chloride and'consisting essentially of alkali ions, nickel-ammonium ions, hydroxyl ions, and chloride ions, and maintaining a v cathode current density of at lease 20 amperes per square foot. 1 1

I0 5. A method of producing nickel in finely divided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and'a nickel-bearinguanode, an alkaline aqueous solution consisting essentially of ala kali ions, nickel-ammonium ions, hydroxyl ions,

and chloride ions, the alkalinity of which solution is equivalent to from 1 to 3 grams of sodium hydroxideper liter and containing at least originally from 200 to 300 grams per liter of ammoni- 40 um chloride and maintaining a cathode current density of at least 20 amperes per square foot.

A 6. A method of producing nickel in finely divided form whichvcomprises subjecting to elec- 1 trolysis in an electrolytic cell in the presence of 5 a cathode and a nickel-bearing anode an alkaline aqueous solution containing at least orig inally from 200 to 300 grams per liter of ammonium chloride and consisting essentially of alkali ions, nickel-ammonium ions, hydroxyl ions, and so chloride ions, maintaining a cathode current density of from 20 to 120 amperes per square'foot and maintaining an anode current density of from 10 to 20 amperes per square foot.

I, A method of producing nickel in finely di- 55 vided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solution containing at least crisinally from 200 to 300 grams per liter of ammoco nium chloride and consisting essentially of alkali ions, nickel-ammonium ions, hydroxyl ions, and

chloride ions. maintaining the temperature of the electrolyte at from 20 to C., and maintaining a cathode current density of from 20 to 120 amperes per square foot. I 5

8. A method of producing nickel in finely divided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solution containing at least origi0 inally from 200 to 300 grams per liter of ammonium chloride and consisting essentially of alkali ions, nickel-ammonium ions, hydroxyl ions, and

chloride ions, maintaining a cathode current a density of at least 20 amperes per square foot 1.5 and regulating the ratio of the anode surface in contact with the solution to the cathode surface in contact with the solution so that nickel de-'- posits at the cathode at substantially the same rate that it goes into solution at the anode. 20

9. A method of producing nickel in finely divided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of I a cathode and in the presence of an insoluble anode and a nickel-bearing anode, an alkaline 25 aqueous solution containing at least originally from 200 to 300 grams per liter of ammonium chloride and consisting essentially of alkali ions,

I nickel-ammonium ions, hydroxyl ions, and chloride ions, maintaining a cathode current density 80 of at least 20 amperes per square foot and regulating the rate at which the nickel goes into solution at the anode by regulating the ratio of the exposed surface of the nickel-bearing anode to the exposed surface of the insoluble anode. 5

10. A method of producing nickel in finely divided form which comprises subjecting to electrolysis in an electrolytic cell in the presence of a cathode and a nickel-bearing anode, an alkaline aqueous solution containing at least orig- 40 inally from 200 tc300 grams per liter of ammonium chloride and consisting essentially of alkali ions, nickel-ammonium ions, hydrosyl ions, and chloride ions, maintaining a cathode current density of at least 20 amperes per square'foot during electrolysis, and maintaining a relatively high ratio of nickel-ammonium ions to nickel ions in said solution during electrolysis.

11. A method of producing nickel in finely divided form which comprises subjecting to elec- I trolysis in an electrolytic cell having a cathode therein an alkaline aqueous solution of ammonium chloride consisting essentiallyof alkali ions, nickel ions, nickel-ammonium ions, hydroxyl ions, andchloride ions, and maintaining the proportion of nickel-ammonium ions-to nickel ions. in said solutionreiatively high during electrolysis, whereby the nickel tends to deposit at the cathode in finely divided form.

crrannns LEIGH MAN'I'ELL. 

